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1. Harvester ant colonies differ in collective behavioural plasticity to regulate water loss

   https://doi.org/10.1098/rsos.230726  

   Gordon, D. M. ; Steiner, E. ; Das, Biplabendu ; Walker, N. S. ( September 2023 , Royal Society Open Science)

   Collective behavioural plasticity allows ant colonies to adjust to changing conditions. The red harvester ant (Pogonomyrmex barbatus), a desert seed-eating species, regulates foraging activity in response to water stress. Foraging ants lose water to evaporation. Reducing foraging activity in dry conditions sacrifices food intake but conserves water. Within a year, some colonies tend to reduce foraging on dry days while others do not. We examined whether these differences among colonies in collective behavioural plasticity persist from year to year. Colonies live 20–30 years with a single queen who produces successive cohorts of workers which live only a year. The humidity level at which all colonies tend to reduce foraging varies from year to year. Longitudinal observations of 95 colonies over 5 years between 2016 and 2021 showed that differences among colonies, in how they regulate foraging activity in response to day-to-day changes in humidity, persist across years. Approximately 40% of colonies consistently reduced foraging activity, year after year, on days with low daily maximum relative humidity; approximately 20% of colonies never did, foraging as much or more on dry days as on humid days. This variation among colonies may allow evolutionary rescue from drought due to climate change.

    

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2. Colony‐level behavioural variation correlates with differences in expression of the foraging gene in red imported fire ants

   https://doi.org/10.1111/mec.14347  

   Bockoven, Alison_A ; Coates, Craig_J ; Eubanks, Micky_D ( October 2017 , Molecular Ecology)

   Among social insects, colony‐level variation is likely to be widespread and has significant ecological consequences. Very few studies, however, have documented how genetic factors relate to behaviour at the colony level. Differences in expression of theforaginggene have been associated with differences in foraging and activity of a wide variety of organisms. We quantified expression of the red imported fire antforaginggene (sifor) in workers from 21 colonies collected across the natural range of Texas fire ant populations, but maintained under standardized, environmentally controlled conditions. Colonies varied significantly in their behaviour. The most active colonies had up to 10 times more active foragers than the least active colony and more than 16 times as many workers outside the nest. Expression differences among colonies correlated with this colony‐level behavioural variation. Colonies with highersiforexpression in foragers had, on average, significantly higher foraging activity, exploratory activity and recruitment to nectar than colonies with lower expression. Expression ofsiforwas also strongly correlated with worker task (foraging vs. working in the interior of the nest). These results provide insight into the genetic and physiological processes underlying collective differences in social behaviour. Quantifying variation in expression of theforaginggene may provide an important tool for understanding and predicting the ecological consequences of colony‐level behavioural variation.

    

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3. Metabolic rate shapes differences in foraging efficiency among honeybee foragers

   https://doi.org/10.1093/beheco/arac090  

   Cassano, Julian ; Naug, Dhruba ( September 2022 , Behavioral Ecology)

   Metabolic rate is the rate at which organisms process energy and is often considered as the fundamental driver of life history processes. The link between metabolic rate and life history is critically mediated via foraging, which shapes the energy acquisition patterns of an individual. This predicts that individuals with different metabolic rates likely vary in their foraging strategies, although such a link has rarely been empirically investigated in the context of optimal foraging theory—a powerful framework for understanding how animals maximize their foraging returns. Many central place foragers such as honeybees maximize their energetic efficiency rather than the rate of energetic gain, given the critical role of energetic costs in foraging decisions. We therefore tested if individuals with low and high metabolic rates differ in efficiency maximization, using genetic lines of honeybees with different metabolic rates. Our results show that low metabolic rate foragers visit more flowers during a foraging trip and have a higher energetic efficiency than high metabolic rate foragers in both low and high resource conditions. We discuss the significance of these results in the context of division of labor and the adaptive role of phenotypic diversity in metabolic rate in a social insect colony.

    

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4. Successful Long-Distance Breeding Range Expansion of a Top Marine Predator

   https://doi.org/10.3389/FEVO.2021.620103  

   Henry, Robert William ; Shaffer, Scott A. ; Antolos, Michelle ; Félix-Lizárraga, María ; Foley, David G. ; Hazen, Elliott L. ; Tremblay, Yann ; Costa, Daniel P. ; Tershy, Bernie R. ; Croll, Donald A. ( May 2021 , Frontiers in Ecology and Evolution)

   Little is known about the effects of large-scale breeding range expansions on the ecology of top marine predators. We examined the effects of a recent range expansion on the breeding and foraging ecology of Laysan albatrosses ( Phoebastria immutabilis ). Laysan albatrosses expanded from historical breeding colonies in the Central Pacific Ocean to the Eastern Pacific Ocean around central Baja California, Mexico, leading to a 4,000-km shift from colonies located adjacent to the productive transition zone in the Central Pacific to colonies embedded within the eastern boundary current upwelling system of the Eastern Pacific California Current. We use electronic tagging and remote sensing data to examine the consequences of this range expansion on at-sea distribution, habitat use, foraging habitat characteristics, and foraging behavior at sea by comparing birds from historic and nascent colonies. We found the expansion resulted in distinct at-sea segregation and differential access to novel oceanographic habitats. Birds from the new Eastern Pacific colony on Guadalupe Island, Mexico have reduced ranges, foraging trip lengths and durations, and spend more time on the water compared to birds breeding in the Central Pacific on Tern Island, United States. Impacts of the range expansion to the post-breeding season were less pronounced where birds maintained some at-sea segregation but utilized similar habitat and environmental variables. These differences have likely benefited the Eastern Pacific colony which has significantly greater reproductive output and population growth rates. Laysan albatrosses have the plasticity to adapt to distinctly different oceanographic habitats and also provide insight on the potential consequences of range shifts to marine organisms. 

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5. Birds of a Feather Flock Together: Extent of Long-Term Consistency of Colony-Size Choice in Cliff Swallows

   https://doi.org/10.3389/fevo.2022.860407  

   Brown, Charles R. ; Hannebaum, Stacey L. ( March 2022 , Frontiers in Ecology and Evolution)

   Explaining why animal groups vary in size is a fundamental problem in behavioral ecology. One hypothesis is that life-history differences among individuals lead to sorting of phenotypes into groups of different sizes where each individual does best. This hypothesis predicts that individuals should be relatively consistent in their use of particular group sizes across time. Little is known about whether animals’ choice of group size is repeatable across their lives, especially in long-lived species. We studied consistency in choice of breeding-colony size in colonially nesting cliff swallows ( Petrochelidon pyrrhonota ) in western Nebraska, United States, over a 32-year period, following 6,296 birds for at least four breeding seasons. Formal repeatability of size choice for the population was about 0.41. About 45% of individuals were relatively consistent in choice of colony size, while about 40% varied widely in the colony size they occupied. Birds using the smaller and larger colonies appeared more consistent in size use than birds occupying more intermediate sized colonies. Consistency in colony size was also influenced by whether a bird used the same physical colony site each year and whether the site had been fumigated to remove ectoparasites. The difference between the final and initial colony sizes for an individual, a measure of the net change in its colony size over its life, did not significantly depart from 0 for the dataset as a whole. However, different year-cohorts did show significant net change in colony size, both positive and negative, that may have reflected fluctuating selection on colony size among years based on climatic conditions. The results support phenotypic sorting as an explanation for group size variation, although cliff swallows also likely use past experience at a given site and the extent of ectoparasitism to select breeding colonies. 

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